The present invention is directed to an interfacing unit for an international-type coin-operated pay telephone, for example that manufactured by Sodeco, Ltd. of Switzerland, and commonly referred to as a Landis-Gyr international-type coin operated telephone. European, and other international, pay-telephone systems differ from their U.S. counterpart in that the telephone system's central office determines the consumption of the initial coins inserted into the coin-operated telephone via the generation of periodic tone-bursts, commonly within a 12K to 16k range. The frequency of the generation of these tone-bursts by the central office determines the frequency of the debiting at the payphone terminal of the coins inserted. Therefore, when making a long distance call that is more expensive than another long distance call, the central office will generate more frequent tone-bursts to the international-type coin-operated telephone, thereby debiting the terminal more frequently in the base coin-units of that particular country.
It is known to retrofit a conventional, U.S.-type, coin-operated telephone, such that the local payphone terminal is equipped with tariffing information, by which the payphone is monitored and charged via information stored at the local site. This is achieved by including at the local terminal site a listing of all of the exchanges to which one may make an outgoing call, and a listing of the associated tariff rates. There are retrofitting units that retrofit U.S. payphones such that tariffing is achieved at the local site. However, coin collection is still to be based upon the conventional, U.S. method of generation of reverse-polarity signals by a central office of the land-based, switched telephone-network. It is also known to couple such U.S. payphones to a cellular transceiver via a conventional cellular interface unit.
The present invention is directed to an interfacing unit that is coupled to an "International"-type payphone, such as the Landis-Gyr, coin-operated pay-telephone, which interfacing unit of the invention assumes all of the functions of the central office, so that private payphones may be readily and easily provided at any chosen site, whether such payphone be coupled directly to the land-based, switched telephone network, or be coupled to a cellular, or other radio, telephone system.